Method of making a flexible letterpress mat

ABSTRACT

A first portion of a sheet of thermoplastic material is placed on the face of an engraved master plate, and the plate and sheet are positioned between the platens of a hydraulic press. The first portion of the sheet and the master plate are pre-heated and are then pressed together to mold an impression of the face within the first portion of the sheet. The master plate and sheet portion are cooled while the pressure is maintained, after which the pressure is released and the sheet is shifted laterally a precise predetermined distance relative to the master plate while maintaining the angular orientation of the sheet, to position a second portion of the sheet over the face of the master plate. The steps of pre-heating, pressing, cooling and releasing are then repeated to produce a flexible mat having a pair of identical impressions in precise spaced relation and corresponding angular orientation. One or more metal layers are electrolytically deposited on the mat, and the resulting thin sheet of deposited metal is separated from the mat and laminated to a pre-curved reinforcing plate which is trimmed along its edge.

United States Patent Bunting et a1.

[ 1' June 6, 1972 [54] METHOD OF MAKING A FLEXIBLE LETTERPRESS MAT [72]Inventors: Charles W. Bunting; David P. Groeber;

Louis W. Pettlo, all of Dayton, Ohio [73] Assignee: McCall Corporation,New York, NY.

[22] Filed: Oct. 26, 1970 [21] Appl. N0.: 83,737

Related US. Application Data [62] Division of Ser. No. 663,858, Aug. 28,1967, Pat. No.

3,532,587 10/1970 Ungar et a1. ..l56/249 X Primary Examiner- Carl D.Quarforth Assistant Examiner-Stephen J. Leche'rt, J r.Attorney-Marechal, Biebel, French & Bugg [57] ABSTRACT A first portionof a sheet of thermoplastic material is placed on the face of anengraved master plate, and the plate and sheet are positioned betweenthe platens of a hydraulic press. The first portion of the sheet and themaster plate are pre-heated and are then pressed together to mold animpression of the face within the first portion of the sheet. The masterplate and sheet portion are cooled while the pressure is maintained,after which the pressure is released and the sheet is shifted laterallya precise predetermined distance relative to the master plate whilemaintaining the angular orientation of the sheet, to position a secondportion of the sheet over the face of the master plate. The steps ofpre-heating, pressing, cooling and releasing are then repeated toproduce a flexible mat having a pair of identical impressions in precisespaced relation and corresponding angular orientation. One or more metallayers are electrolytically deposited on the mat, and the resulting thinsheet of deposited metal is separated from the mat and laminated to apre-curved reinforcing plate which is trimmed along its edge.

4 Claims, 10 Drawing Figures PATENTEUJUH 6 I972 SHEET B) W, 7 Mi CHARLESW. HUNTING, DAVID P. GROEBER 8 LOUIS W. PETTLO 1 METHOD or MAKING AFLEXIBLE LETIERPRESS MAT RELATED APPLICATIONS BACKGROUND OF THEINVENTION In the production of part-cylindrical plates for mounting onthe rolls of a letterpress, a flexible matrix or mat is made by firstpre-heating a flat original engraved plate within a device commonlyreferred to as a clamshell having internal passageways through which aheating fluid such as steam is circulated. After pre-heating, theengraved plate is removed from the clamshell and a sheet of vinyl isplaced on the mat with an overlay of a resilient blanket, and thesandwiched assembly of the plate, vinyl sheet and blanket is insertedwithin a hydraulic press where substantial pressure is applied to moldin the vinyl sheet an impression of the engraved plate. The sheet andthe engraved plate are then cooled within the press while pressure ismaintained to form a flexible vinyl mat. One or more metal layers areelectrolytically deposited on the mat and the thin sheet of depositedmetal is then separated from the vinyl sheet to form a flexibleelectrotype which is laminated to a pre-curved reinforcing mat and thislaminated assembly is trimmed to form the letterpress plate.

It has been found desirable to avoid the transfer operation of thepre-heated engraved plate from the clamshell to the high pressure pressafter adding the vinyl sheet and blanket to increase efficiency inproducing a mat and to avoid heat loss from the plate during thetransfer. Furthermore, for efficiently printing some smaller books ormagazines, it is frequently desirable to form a mat having a pair ofidentical impressions in precise registration for producing a two-onletterpress plate on which two impressions are spaced circumferentiallyin relation to the roll of the letterpress on which the plate ismounted.

SUMMARY OF THE INVENTION The present invention is directed to animproved method and apparatus for efficiently producing a flexible vinylmat and which is especially suited for forming a two-on mat or a four-onmat having corresponding pairs of identical impressions all in preciseregistration. Thus the method and apparatus of the invention provide forefficiently constructing either two-on or four-on letterpress plates andthereby substantially reduce the time required to mount and align a setof plates on the plate cylinders of the letterpress for a particularprinting job.

According to a preferred embodiment of the invention, a two on mat isproduced by securing an engraved master plate to the center section of aflat lower press member which slidably supports a U-shaped frame towhich is secured a sheet of vinyl. Cooling fluid is circulated throughpassageways fonned within each end section of the press member andcooling and heating fluid are alternately circulated through apassageway within the center section directly under the engraved plate.

The lower press member, master plate and the vinyl sheet are carriedinto a hydraulic press where a portion of the vinyl sheet is held inlight contact with the engraved face of the master plate by a resilientblanket mounted on an upper press member while the master plate andvinyl sheet are pre-heated by circulating steam through the centersection of the lower press member. After the master plate reaches apredetermined temperature, the sheet of vinyl is pressed against theengraved face of the plate by raising the lower press member toward theupper press member.

As the high pressure is being applied, cool water is circulated throughthe center section of the lower press member in place of the steam tocool the corresponding portion of the vinyl sheet while the remainingportion of the vinyl sheet is maintained cool by the water beingcirculated through the adjacent end section of the lower press member.After one impression is made in the vinyl sheet, the sheet is shifted apredetermined distance by sliding the frame laterally and a secondimpression is formed within the vinyl sheet by repeating the aboveprocedure. As a result, two identical impressions can be quickly formedwithin the'sheet with the impression disposed in precise registration.

Other features and advantages of the invention will be apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view ofapparatus for forming a flexible mat in accordance with the invention; 1

FIG. 2 is a perspective view of a vinyl sheet and the upper and lowerpress members forming a part of the apparatus shown in FIG. 1;

FIG. 3 is a plan view of the lower press member with two engraved platesmounted thereon;

FIG. 4 is an elevation view of the upper and lower press members astaken generally on the line 4-4 of FIG. 3;

FIG. 5 is a section of the lower press member taken generally on theline 5-5 of FIG. 3;

FIG. 6 is a side elevational view of the upper press member and asection of the lower press member taken generally on the line 66 of FIG.3;

FIG. 7 is a schematic flow diagram showing the circulation of heatingand cooling fluid throughthe lower press;

' FIG. 8 is a view of a typical mat formed in accordance with theinvention and having two sets of two-on impressions;

FIG. 9 is a fragmentary section of the lower press member as takengenerally on the line 99 of FIG. 5; and

FIG. 10 is an enlarged fragmentary section as taken on the line 10-10 ofFIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a hydraulic moldingpress 15 of the type manufactured by Ostrander-Seymour Company, MelrosePark, Illinois, and generally includes a base 16 which supports a table18 movable horizontally between an extended position (FIG. 1) and aretracted position (not shown) under a head portion 20 where the tableis moved vertically by a hydraulic cylinder (not shown) mounted on thebase 16. An automatic recorder controller 22 is mounted on the headportion 20 and is connected to control the horizontal and verticalmovements of the table 18 in accordance with a pre-selected temperaturesequence as explained later.

In accordance with the invention, a lower press member 25 in the form ofa rectangular plate is mounted on the upper surface of the table 18. Thepress member 25 includes a base portion 26 (FIG. 6) having a pair ofparallel spaced slots 28 (FIG. 5) which divide the base portion 26 intoa pair of end sections 29 on opposite sides of a center section 30. Astrip 32 of insulation material, such as a strip ofpolytetrafluorethylene, is mounted within each of the slots 28 as shownin FIG. 10.

The base section 26 of the press plate 25 is provided with alongitudinal flat edge surface 34 (FIG. 6) to which an edge portion 35is secured by a series of screws 36. A longitudinally extending slot 38of rectangular cross section is formed within the edge section 35 havingthe surface 34 as one side, and a corresponding parallel spaced slot 39formed within the base portion 26. A U-shaped frame 45 (FIG. 3) includesa pair of parallel spaced legs 46 which are slidably mounted within thecorresponding slots 38 and 39 within the press member 25. The legs 46are rigidly connected by a bar 48 and each leg is provided with alongitudinally extending slot 49.

A threaded stud 55 (FIGS. 3 and 6) extends through the base portion 26and has an inner end portion 56 which is received within thecorresponding slot 49. Another threaded stud 55 extends through the edgeportion 35 of the lower press member 25 and has an inner portion 56received within the slot 49 of the other leg 46 so that the studs 55cooperate to retain the frame 45 on the lower press member 25. A locknut 58 is mounted on each of the studs 55 for securing the studs rigidlyto the lower press member after it is properly adjusted.

A vertically extending pin 60-(FIG. 3) is mounted on the end portion ofeach leg 46 of the frame 45, and a pair of L- shaped stop members 62 aremounted on one end of the press member 25 by screws 63 and extend intothe slots 38 and 39 for engaging the end surfaces of the legs 46 andthereby limit the movement of the frame 45 to the right (FIG. 3). Thestuds 55 limit the movement of the frame to the left.

' Referring to FIGS. and 10, the center section 30 of the lower pressmember 25 has a flat top surface 65 which is spaced slightly below thecorresponding top surface 66 of the adjacent end sections 29 and forms arecess between the insulation strips 32 for receiving two originalormaster plates P, and P each having an engraved face. Each master plateis secured to the center section 30 by a pair of screws 68 and theengraved face of each master plate projects slightly above the topsurfaces 66 of the end sections 29 by approximately 0.010 inch.

Referring to FIG. 9, each end section 29 and the center section 30 ofthe press member 25 is provided with a series of parallel spacedpassageways 70 which extend laterally between the slots 38 and 39 andare connected on opposite ends by longitudinally extending passageways72. A series of plugs 74 are press-fitted into the passageways 72 and aseries of threaded plugs 76 close the corresponding ends of thepassageways 70 to form a serpentine-like flow path between an inlet port77 and an outlet port 78. Referring to FIG. 6, the inlet and outletports are formed within the press member 25 under the rail 39 and areconnected to the adjacent passageways 72 by short vertically extendingpassageways 80 (FIG. 6) which are closed at the bottom of the pressmember by corresponding plugs 82.

Referring to FIG. 7, the inlet ports 77 of the end sections 29 of thepress member 25 are connected by lines 85 to a water supply line 86through a flexible line 87 and including a manual shutofi valve 88. Thedischarge ports 78 of each end section 29 are connected by lines 90 and91 through a flexible line 92 to a drainline 94 having a check valve 95.The inlet port 77 of the center section 30 of the press member 25 isconnected by a line 97 and a flexible line 98 to a steam supply line.100 in which is mounted solenoid control valve 102, a manual shutoffvalve 103, a pressure gage 104 and a pressure regulator l05..The lines-97 and 98 are also connected to a water supplyline 108 having a checkvalve 109, a solenoid controlled valve 110 and a manual shutoff valve111. The water supply line 108 connects with the .water supply line 86.

- The outlet port'78 of the center section 30 is connected by a line 115 and flexible line 116 to a drain line 1 18 which is normallyconnected to the drain line 94 through a three-way solenoid controlledvalve 120. A condensate line 122 connects the valve 120 to the drain'line 94 on the opposite side of the check valve 95 and is provided witha strainer 124, a steam trap 125 and a check valve 126. The solenoidcontrolled valves 102, I and 120 are actuated by the recorder controller22 which is controlled by a thennocouple 130 mounted within the centersection 30 of the press member 25. Leads 132 connect the thermocouple130 to the controller 135.

Referring to FIGS. 2, 4 and 6, a stationary upper press member 140 inthe form of a rectangular plate, is mounted within the head 20 of thepress and is disposed directly above the center section 30 of the lowerpress member 25 when the table 18 is retracted. The upper press member140 includes end mounting flanges 141 and may be provided with internalpassageways 142 (FIG. 6) corresponding to the 'passageways 70 and 72within the center section 30 of the lower press member 25, for heatingand cooling the upper press member simultaneously with the centersection 30. Ex-

perimentation has shown, however, that the additional heating'andcooling of the upper press member 140 is not necessary to obtainsatisfactory performance of the apparatus.

A resilient rectangular blanket 145, preferably of a rubberfabricmaterial and having a uniform thickness, extends over the bottom flatsurface 146 of the upper press member 140. The blanket has opposite endportions which extend into corresponding grooves 148 formed within thepreset member and the end portions are secured by corresponding clampingbars 149.

To produce a mat with the apparatus constructed in accordance with theinvention, a sheet 155 (FIGS. 2 and 3) of thermoplastic material such asvinyl and having a pair of prepunched holes 156, is mounted on the frame45 so that the pins 60 project into the holes 156. The valve 88 isopened so that cooling water is continuously circulated through the endsections 29 of the lower press member 25 thereby cooling the topsurfaces 66 of the end sections 29.

The recorder controller 22 is manually actuated to initiate apredetermined cycle which begins with retracting the table 18 under thehead 20. The table 18 and lower press member 25 are then moved upwardlywith relatively light pressure so that the sheet 155 of vinyl lightlycontacts the blanket 145 on the upper press member 140 and is therebyheld in light contact with the engraved faces of the master plates P,and P When the table is retracted, it actuates a switch which opens thesolenoid controlled valve 102 and closes the valve 110. When thecontroller 22 senses a temperature rise through the thermocouple 130,valve is actuated to connect return line 118 to the condensate line 122so that steam is circulated through the center section 30 of the lowerpress member 25 which raises the temperature of the master plates P, andP, and the overlying portion of the vinyl sheet 155.

When the center section 30 of the lower press member 25 reaches apredetermined curing temperature, which can be adjustably set, thethermocouple signals the controller 22 which energizes the hydrauliccylinder within the press 15 so that it applies full force upwardly onthe table 18. As a result, the engraves faces of the plates P, and P arepressed into the vinyl sheet thereby producing corresponding impressionsI, and I within the sheet as illustrated'in FIG. 8 on the righthandportion of the sheet 155.

Substantially simultaneously with the: application of full pressure onthe lowerpress member 25 against the upper press member 140, whichproduces a force on the order of twelve tons, therecorder controller 22closes the valve 102, opens the valve 1 10 and actuates the valve 120 sothat the line 1 18 is connected directly to the drain line 94. Thus thetemperature of the center section 30 of the lower press member 25 andthe master plates P, and P and the vinyl sheet 155 begins to drop. Whenthe temperature of the center section 30 reaches a predetermined lowerlimit, which can be adjustably set, the thermocouple 130 signals thecontroller 22 which actuates the hydraulic cylinder in the press 15 tolower the table 18 and thereby release the pressure between the upperand lower press member, after which the table 18 automatically returnsto its extended position as shown in FIG. 1.

After one set of impressions I and I, are formed within the vinyl sheet155 from the master plates P, and P,, the frame 45 and sheet 155 aremoved to the right (FIG. 3) until the ends of the legs 46 engage thestop members 62. In this position, the right-hand portion of the vinylsheet 155 which has the impressions I, and I is positioned adjacent thetop surface 66 of the right end section 29 of the lower press member 25and the left end portion of the sheet is positioned over the engravedfaces of the master plates P, and P The recorder controller 22 isactuated again so that the operational steps of the cycle described inthe preceding paragraphs are repeated automatically which results inproducing a sheet 155 having another set of impressions I and I, (FIG.8) in precise registration to the corresponding first set of impressionsI, and I The sheet 155 is then cut or sheared along the line to producetwo mats each having a pair of identical impressions in preciseregistration. Each mat is then used to produce atwo-on letterpress plateusing the same procedure as mentioned above for producing a plate with asingle impression. That is, one or more metal layers areelectrolytically deposited on each mat. The resulting thin sheet ofdeposited metal is separated from the mat to form a flexible electrotypewhich is laminated to a pre-curved reinforcing mat or plate. The plateis then trimmed to form a letterpress plate.

From the drawings and the above description, it can be seen that theapparatus and method for producing a mat in accordance with theinvention provides several desirable features and advantages. Forexample, by connecting the center section 30 of the lower press member25 to corresponding water and steam supply and discharge lines havingautomatically controlled valves, the center section 30 may be heatedwithin the press for pre-heating the master plates and the vinyl sheetand then cooled while-full pressure is applied between the press membersto produce a mat without requiring the transfer of .the master platefrom a pre-heating clamshell to a molding press. As a result, the timerequired for forming an impression within the vinyl sheet issignificantly reduced. In addition, the cooling under pressure preventsshrinkage of the image.

The slidable frame 45 and its cooperation with the three section lowerpress member 25 also provide important features of the invention. Thatis, the frame 45 provides for shifting the vinyl sheet 155 by a precisepredetermined distance after one impression is made so that a secondidentical impression can be formed within the sheet in preciseregistration with the first impression. The continuous cooling of theend sections 29 is effective to prevent the adjacent portion of theoverlying half portion of the vinyl sheet from being heated when theother half portion is being heated and pressed against the face of themaster plate, and thereby prevents warping and distortion of theadjacent portion of the vinyl sheet.

Instead of producing two two-on mats as shown in FIG. 8, it can be seenthat the master plates P and P could be formed integrally or rigidlyconnected with the corresponding engraved faces in precise registrationso that a four-on" mat could be produced with all of the impressions inprecise registration. A typical application for a four-on mat would befor producing a letterpress plate having two-on" double pageimpressions. By providing an automatic control system as shown I in FIG.7 for circulating steam or water through the center section 30 of thelower press member 25, and controlling the operation of the system by athen'nocouple which senses the temperature of the center section 30,each mat receives the same treatment so that the impressions on each matof a color set will have precisely the same registration and therebysubstantially reduces the time for mounting and positioning the plateson the plate cylinders of the letterpress.

While the method herein described constitutes a preferred embodiment ofthe invention, it is to be understood that the invention is not limitedto this precise method, and that changes may be made therein withoutdeparting from the scope of the invention which is defined in theappended claims.

What is claimed is:

l. A method of making a multiple impression letterpress plate,comprising the steps of positioning a first portion of a sheet ofthermoplastic material in overlying relation with an engraved-like faceof a master plate, positioning said master plate and the overlying firstportion of said sheet between first and second press members of areciprocating press, preheating said master plate and said first portionof said sheet to a predetermined temperature, moving said first andsecond press members together to effect pressing of said first portionof said sheet with a predetermined pressure against said face of saidmaster plate to mold an impression of said face within said firstportion of said sheet, cooling said master plate and said first portionof said sheet, moving said first and second press members apart forreleasing said pressure, shifting said sheet laterally a predetermineddistance relative to said master plate while maintaining precise angularorientation of said sheet relative to said masterplate for positioning asecond portron of said sheet in overlying relation withsaid face of saidmaster plate, repeating said pre-heating, pressing, cooling andreleasing steps to fonn a mat having a pair of identical impressions inprecise spaced relation and corresponding angular orientation and witheach impression conforming to said face of said master plate, coatingmetal onto said mat to form a layer of metal corresponding to theimpressions on said mat, separating said layer of metal from said mat toform a metal sheet having a corresponding pair of identical impressions,and laminating said metal sheet to a curved reinforcing plate.

2. A method as defined in claim 1 including the step of holding saidsheet of thermoplastic material in light contact with said face of saidmaster plate during said preheating by lightly pressing said secondpress member toward said first press member to effect said pre-heatingsaid sheet of thermoplastic material.

3. A method as defined in claim 1 wherein said master plate and eachportion of said sheet are pre-heated by circulating heating fluidthrough a passageway formed in said first press member, and said masterplate and each portion of said sheet are cooled by circulating coolingfluid through said passageway in place of said heating fluid.

4. A method as defined in claim 1 including the steps of cooling saidsecond portion of said thermoplastic sheet during said pre-heating,pressing and cooling of said first portion of said sheet to preventwarping of said second portion of said sheet, and cooling said firstportion of said sheet while preheating, pressing and cooling of saidsecond portion to prevent warpingof said first portion of said sheet.

1. A method of making a multiple impression letterpress plate,comprising the steps of positioning a first portion of a sheet ofthermoplastic material in overlying relation with an engravedlike faceof a master plate, positioning said master plate and the overlying firstportion of said sheet between first and second press members of areciprocating press, preheating said master plate and said first portionof said sheet to a predetermined temperature, moving said first andsecond press members together to effect pressing of said first portionof said sheet with a predetermined pressure against said face of saidmaster plate to mold an impression of said face within said firstportion of said sheet, cooling said master plate and said first portionof said sheet, moving said first and second press members apart forreleasing said pressure, shifting said sheet laterally a predetermineddistance relative to said master plate while maintaining precise angularorientation of said sheet relative to said master plate for positioninga second portion of said sheet in overlying relation with said face ofsaid master plate, repeating said pre-heating, pressing, cooling andreleasing steps to form a mat having a pair of identical impressions inprecise spaced relation and corresponding angular orientation and witheach impression conforming to said face of said master plate, coatingmetal onto said mat to form a layer of metal corresponding to theimpressions on said mat, separating said layer of metal from said mat toform a metal sheet having a corresponding pair of identical impressions,and laminating said metal sheet to a curved reinforcing plate.
 2. Amethod as defined in claim 1 including the step of holding said sheet ofthermoplastic material in light contact with said face of said masterplate during said preheating by lightly pressing said second pressmember toward said first press member to effect said pre-heating saidsheet of thermoplastic material.
 3. A method as defined in claim 1wherein said master plate and each portion of said sheet are pre-heatedby circulating heating fluid through a passageway formed in said firstpress member, and said master plate and each portion of said sheet arecooled by circulating cooling fluid through said passageway in place ofsaid heating fluid.
 4. A method as defined in claim 1 including thesteps of cooling said second portion of said thermopLastic sheet duringsaid pre-heating, pressing and cooling of said first portion of saidsheet to prevent warping of said second portion of said sheet, andcooling said first portion of said sheet while pre-heating, pressing andcooling of said second portion to prevent warping of said first portionof said sheet.